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  1. #1
    Senior Member 135crewchief's Avatar
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    What's the advantage of presta valves?

    What's the advantage of presta valves?

  2. #2
    Senior Member gordyt's Avatar
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    Don't take this as gospel, but I remember reading somewhere that the smaller diameter of presta valves makes for less of a weak spot in the wheel 'cause of the smaller hole.

    --gordy

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    Senior Member MudPie's Avatar
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    Quote Originally Posted by 135crewchief
    What's the advantage of presta valves?
    Maybe a minor advantage - You don't have to work against a spring when you clip on the pump head.

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    you can get a smaller rim with a presta.

  5. #5
    hello roadfix's Avatar
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    You don't have to carry a presta to schrader adapter....
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  6. #6
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    You don't look like a noob.

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    Dog is my co-pilot 2manybikes's Avatar
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    They fit in that little presta size hole in the rim.




    Was there a Monsieur Presta or a Mister Schrader?

  8. #8
    Senior Member jalexei's Avatar
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    My understanding is that the presta valve does a better job sealing with the higher pressures one sees on a bike, as opposed to automobiles, where the schrader standard comes from. Schrader valves are also a bit more susceptible to problems if dirt and gunk get under the plastic cap.

  9. #9
    Senior Member DannoXYZ's Avatar
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    Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
    Last edited by DannoXYZ; 08-04-05 at 10:49 PM.

  10. #10
    hello roadfix's Avatar
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    I thought the centrifical force actually 'forced' the sprung schrader valve to seal even tighter....
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  11. #11
    Senior Member DannoXYZ's Avatar
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    Nope, look at the direction that the valve moves to open and seal. The valve points towards the axle of the wheel. The spring pushes the valve towards the axle to seal. To open the valve, you push it outwards towards the outside of the wheel (towards the tyre), in the same direction centripedal force pushes the valve. Get enough RPMs spinning and you'll open the valve.

  12. #12
    Senior Member jalexei's Avatar
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    I've had a couple instances at Bonneville...
    How sweet it would be to be able to drop that line in a conversation!

  13. #13
    Dog is my co-pilot 2manybikes's Avatar
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    Quote Originally Posted by DannoXYZ
    Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
    I have that problem on my bicycle once in a while too. That's a helpful tip, thanks.

  14. #14
    dangerous with tools halfbiked's Avatar
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    less likelihood of bursting tubes through over-enthusiastic use of air compressor to fill tires.




    though this is less of an issue with these 100+ psi tubes...

  15. #15
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    Quote Originally Posted by DannoXYZ
    Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
    That's why Formula 1 cars use presta !

    On a serious note, that's interesting. Never thought of it...
    A California ordinance states that a $500 fine will be given to anyone who detonates a nuclear device within city limits.

  16. #16
    hello roadfix's Avatar
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    Quote Originally Posted by DannoXYZ
    Nope, look at the direction that the valve moves to open and seal. The valve points towards the axle of the wheel. The spring pushes the valve towards the axle to seal. To open the valve, you push it outwards towards the outside of the wheel (towards the tyre), in the same direction centripedal force pushes the valve. Get enough RPMs spinning and you'll open the valve.
    Yep, you're absolutely right... For some reason, I had imagined the valve sticking outward in a centrifuge!...stupid me...
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  17. #17
    Senior Member
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    Quote Originally Posted by DannoXYZ
    Yeah, the presta uses an active force to shut the valve, whereas the shraeder only uses the spring-pressure. I've had a couple instances at Bonneville where the rotational inertia of the valve spinning around actually forces the schraeder innards open against the spring. Not fun losing tire-pressure at 185mph... The solution was to lock-tite on some steel valve-stem caps.
    The next time I get my bike up to 185 mph I'll feel much more confident with my presta valves.

    Al

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